Either there are two typos in the sentence, or it is the reproduction of Bavarian colloquial speech (plus still a typo).
The correct sentence in standard German would be:
Unser Konversationskurs ist genau das Richtige für Sie.
So, the article should be »das« and the following noun should be capitalized.
In some Bavarian dialects the neuter article in nominative case is not »das«, but »des«. So in colloquial speech you sometimes might hear exactly this sentence. This is not really wrong, it is just non-standard German. You will often hear it in the south of Germany and in Austria, but it is very rare, that this will be written.
There are no binding orthographic rules for writing dialects or colloquial speech. But no matter which set of rules you may invent for writing this, it should be consistent. So either you write both nouns capitalized (»Konversationskurs« and »Richtige«) or you use all lowercase letters for both nouns (»konversationskurs« and »richtige«). Later is not recommended. Even when writing colloquial speech, it would be wise to apply as many standard orthographic rules as possible.
So if this really was Bavarian colloquial speech, you should write it this way:
Unser Konversationskurs ist genau des Richtige für Sie.
But my guess is, that it should be standard German and contains two typos.
